The present invention relates to a crankshaft for a hermetic compressor, and more specifically to a new configuration for the axial bearing (thrust bearing) of the crankshaft eccentric portion.
Rotary rolling piston compressors, for example, have in the crankshaft an eccentric portion to give the rotation and translation movement to the rolling piston. This eccentric portion (or eccentric only) is mounted between the walls of a pair of bearing so that, in operation, it tends to ride against one of these bearings, and more commonly on the sub bearing. The bearing that operates to axially constrain the crankshaft is hereafter called an axial bearing.
With the shaft rotation during compressor operation, the eccentric bears against the wall of the cover or axial bearing. This causes energy loss by friction which obviously increases the compressor power consumption. This is particularly true for upright compressors, both rotary and reciprocal, where all rotor weight of the electric motor bears against the axial bearing.
Even in horizontal compressors the loss by friction can happen, since the magnetic force of the electric motor axially pushes the shaft and, therefore, makes the piston eccentric bear against the axial bearing wall. An attempt to solve this problem in reciprocating compressors by the use of rolling bearings which always are, for any type of compressor, an expensive and problematic solution. Another attempt to reduce the loss by friction is through the insertion of washers of various materials of a smaller friction coefficient in the axial bearing which also is an expensive and complicated process.